Added Tony's defer_foo patch to dnsdb lookups.
[exim.git] / src / src / lookups / dnsdb.c
1 /* $Cambridge: exim/src/src/lookups/dnsdb.c,v 1.6 2004/12/20 15:24:28 ph10 Exp $ */
2
3 /*************************************************
4 * Exim - an Internet mail transport agent *
5 *************************************************/
6
7 /* Copyright (c) University of Cambridge 1995 - 2004 */
8 /* See the file NOTICE for conditions of use and distribution. */
9
10 #include "../exim.h"
11 #include "lf_functions.h"
12 #include "dnsdb.h"
13
14
15
16 /* Ancient systems (e.g. SunOS4) don't appear to have T_TXT defined in their
17 header files. */
18
19 #ifndef T_TXT
20 #define T_TXT 16
21 #endif
22
23 /* Table of recognized DNS record types and their integer values. */
24
25 static char *type_names[] = {
26 "a",
27 #if HAVE_IPV6
28 "aaaa",
29 #ifdef SUPPORT_A6
30 "a6",
31 #endif
32 #endif
33 "cname",
34 "mx",
35 "mxh",
36 "ns",
37 "ptr",
38 "srv",
39 "txt",
40 "zns"
41 };
42
43 static int type_values[] = {
44 T_A,
45 #if HAVE_IPV6
46 T_AAAA,
47 #ifdef SUPPORT_A6
48 T_A6,
49 #endif
50 #endif
51 T_CNAME,
52 T_MX,
53 T_MXH, /* Private type for "MX hostnames" */
54 T_NS,
55 T_PTR,
56 T_SRV,
57 T_TXT,
58 T_ZNS /* Private type for "zone nameservers" */
59 };
60
61
62 /*************************************************
63 * Open entry point *
64 *************************************************/
65
66 /* See local README for interface description. */
67
68 void *
69 dnsdb_open(uschar *filename, uschar **errmsg)
70 {
71 filename = filename; /* Keep picky compilers happy */
72 errmsg = errmsg; /* Ditto */
73 return (void *)(-1); /* Any non-0 value */
74 }
75
76
77
78 /*************************************************
79 * Find entry point for dnsdb *
80 *************************************************/
81
82 /* See local README for interface description. The query in the "keystring" may
83 consist of a number of parts.
84
85 (a) If the first significant character is '>' then the next character is the
86 separator character that is used when multiple records are found. The default
87 separator is newline.
88
89 (b) If the next sequence of characters is 'defer_FOO' followed by a comma,
90 the defer behaviour is set to FOO. The possible behaviours are: 'strict', where
91 any defer causes the whole lookup to defer; 'lax', where a defer causes the
92 whole lookup to defer only if none of the DNS queries succeeds; and 'never',
93 where all defers are as if the lookup failed. The default is 'lax'.
94
95 (c) If the next sequence of characters is a sequence of letters and digits
96 followed by '=', it is interpreted as the name of the DNS record type. The
97 default is "TXT".
98
99 (d) Then there follows list of domain names. This is a generalized Exim list,
100 which may start with '<' in order to set a specific separator. The default
101 separator, as always, is colon. */
102
103 int
104 dnsdb_find(void *handle, uschar *filename, uschar *keystring, int length,
105 uschar **result, uschar **errmsg, BOOL *do_cache)
106 {
107 int rc;
108 int size = 256;
109 int ptr = 0;
110 int sep = 0;
111 int defer_mode = PASS;
112 int type = T_TXT;
113 int failrc = FAIL;
114 uschar *outsep = US"\n";
115 uschar *equals, *domain;
116 uschar buffer[256];
117
118 /* Because we're the working in the search pool, we try to reclaim as much
119 store as possible later, so we preallocate the result here */
120
121 uschar *yield = store_get(size);
122
123 dns_record *rr;
124 dns_answer dnsa;
125 dns_scan dnss;
126
127 handle = handle; /* Keep picky compilers happy */
128 filename = filename;
129 length = length;
130 do_cache = do_cache;
131
132 /* If the string starts with '>' we change the output separator */
133
134 while (isspace(*keystring)) keystring++;
135 if (*keystring == '>')
136 {
137 outsep = keystring + 1;
138 keystring += 2;
139 while (isspace(*keystring)) keystring++;
140 }
141
142 /* Check for a defer behaviour keyword. */
143
144 if (strncmpic(keystring, US"defer_", 6) == 0)
145 {
146 keystring += 6;
147 if (strncmpic(keystring, US"strict", 6) == 0)
148 {
149 defer_mode = DEFER;
150 keystring += 6;
151 }
152 else if (strncmpic(keystring, US"lax", 3) == 0)
153 {
154 defer_mode = PASS;
155 keystring += 3;
156 }
157 else if (strncmpic(keystring, US"never", 5) == 0)
158 {
159 defer_mode = OK;
160 keystring += 5;
161 }
162 else
163 {
164 *errmsg = US"unsupported dnsdb defer behaviour";
165 return DEFER;
166 }
167 while (isspace(*keystring)) keystring++;
168 if (*keystring++ != ',')
169 {
170 *errmsg = US"dnsdb defer behaviour syntax error";
171 return DEFER;
172 }
173 while (isspace(*keystring)) keystring++;
174 }
175
176 /* If the keystring contains an = this must be preceded by a valid type name. */
177
178 if ((equals = Ustrchr(keystring, '=')) != NULL)
179 {
180 int i, len;
181 uschar *tend = equals;
182
183 while (tend > keystring && isspace(tend[-1])) tend--;
184 len = tend - keystring;
185
186 for (i = 0; i < sizeof(type_names)/sizeof(uschar *); i++)
187 {
188 if (len == Ustrlen(type_names[i]) &&
189 strncmpic(keystring, US type_names[i], len) == 0)
190 {
191 type = type_values[i];
192 break;
193 }
194 }
195
196 if (i >= sizeof(type_names)/sizeof(uschar *))
197 {
198 *errmsg = US"unsupported DNS record type";
199 return DEFER;
200 }
201
202 keystring = equals + 1;
203 while (isspace(*keystring)) keystring++;
204 }
205
206 /* Initialize the resolver in case this is the first time it has been used. */
207
208 dns_init(FALSE, FALSE);
209
210 /* The remainder of the string must be a list of domains. As long as the lookup
211 for at least one of them succeeds, we return success. Failure means that none
212 of them were found.
213
214 The original implementation did not support a list of domains. Adding the list
215 feature is compatible, except in one case: when PTR records are being looked up
216 for a single IPv6 address. Fortunately, we can hack in a compatibility feature
217 here: If the type is PTR and no list separator is specified, and the entire
218 remaining string is valid as an IP address, set an impossible separator so that
219 it is treated as one item. */
220
221 if (type == T_PTR && keystring[0] != '<' &&
222 string_is_ip_address(keystring, NULL) > 0)
223 sep = -1;
224
225 /* Now scan the list and do a lookup for each item */
226
227 while ((domain = string_nextinlist(&keystring, &sep, buffer, sizeof(buffer)))
228 != NULL)
229 {
230 uschar rbuffer[256];
231 int searchtype = (type == T_ZNS)? T_NS : /* record type we want */
232 (type == T_MXH)? T_MX : type;
233
234 /* If the type is PTR, we have to construct the relevant magic lookup
235 key. This code is now in a separate function. */
236
237 if (type == T_PTR)
238 {
239 dns_build_reverse(domain, rbuffer);
240 domain = rbuffer;
241 }
242
243 DEBUG(D_lookup) debug_printf("dnsdb key: %s\n", domain);
244
245 /* Do the lookup and sort out the result. There are two special types that
246 are handled specially: T_ZNS and T_MXH. The former is handled in a special
247 lookup function so that the facility could be used from other parts of the
248 Exim code. The latter affects only what happens later on in this function,
249 but for tidiness it is handled in a similar way. If the lookup fails,
250 continue with the next domain. In the case of DEFER, adjust the final
251 "nothing found" result, but carry on to the next domain. */
252
253 rc = dns_special_lookup(&dnsa, domain, type, NULL);
254
255 if (rc == DNS_NOMATCH || rc == DNS_NODATA) continue;
256 if (rc != DNS_SUCCEED)
257 {
258 if (defer_mode == DEFER) return DEFER; /* always defer */
259 else if (defer_mode == PASS) failrc = DEFER; /* defer only if all do */
260 continue; /* treat defer as fail */
261 }
262
263 /* Search the returned records */
264
265 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
266 rr != NULL;
267 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
268 {
269 if (rr->type != searchtype) continue;
270
271 /* There may be several addresses from an A6 record. Put the configured
272 separator between them, just as for between several records. However, A6
273 support is not normally configured these days. */
274
275 if (type == T_A ||
276 #ifdef SUPPORT_A6
277 type == T_A6 ||
278 #endif
279 type == T_AAAA)
280 {
281 dns_address *da;
282 for (da = dns_address_from_rr(&dnsa, rr); da != NULL; da = da->next)
283 {
284 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
285 yield = string_cat(yield, &size, &ptr, da->address,
286 Ustrlen(da->address));
287 }
288 continue;
289 }
290
291 /* Other kinds of record just have one piece of data each, but there may be
292 several of them, of course. */
293
294 if (ptr != 0) yield = string_cat(yield, &size, &ptr, outsep, 1);
295
296 if (type == T_TXT)
297 {
298 yield = string_cat(yield, &size, &ptr, (uschar *)(rr->data+1),
299 (rr->data)[0]);
300 }
301 else /* T_CNAME, T_MX, T_MXH, T_NS, T_SRV, T_PTR */
302 {
303 int num;
304 uschar s[264];
305 uschar *p = (uschar *)(rr->data);
306
307 if (type == T_MXH)
308 {
309 /* mxh ignores the priority number and includes only the hostnames */
310 GETSHORT(num, p); /* pointer is advanced */
311 }
312 else if (type == T_MX)
313 {
314 GETSHORT(num, p); /* pointer is advanced */
315 sprintf(CS s, "%d ", num);
316 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
317 }
318 else if (type == T_SRV)
319 {
320 int weight, port;
321 GETSHORT(num, p); /* pointer is advanced */
322 GETSHORT(weight, p);
323 GETSHORT(port, p);
324 sprintf(CS s, "%d %d %d ", num, weight, port);
325 yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
326 }
327
328 rc = dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen, p,
329 (DN_EXPAND_ARG4_TYPE)(s), sizeof(s));
330
331 /* If an overlong response was received, the data will have been
332 truncated and dn_expand may fail. */
333
334 if (rc < 0)
335 {
336 log_write(0, LOG_MAIN, "host name alias list truncated: type=%s "
337 "domain=%s", dns_text_type(type), domain);
338 break;
339 }
340 else yield = string_cat(yield, &size, &ptr, s, Ustrlen(s));
341 }
342 } /* Loop for list of returned records */
343 } /* Loop for list of domains */
344
345 /* Reclaim unused memory */
346
347 store_reset(yield + ptr + 1);
348
349 /* If ptr == 0 we have not found anything. Otherwise, insert the terminating
350 zero and return the result. */
351
352 if (ptr == 0) return failrc;
353 yield[ptr] = 0;
354 *result = yield;
355 return OK;
356 }
357
358 /* End of lookups/dnsdb.c */